I also recall AA warning back in 2016 that they were expecting some short term issues stemming from the introduction of “domestic Premium Economy” (I assume from elites), but I don’t think we’ve heard anything else since. Perhaps that was shelved with the departure of Kirby.
Domestic premium economy has not been shelved, but it's not a "plan", Instead, it's what will happen if longhaul planes that have true premium economy are put on domestic routes. In that sense, it can't be avoided.
However: AA has precedent for booking a whole multi-cabin plane as coach in certain circumstances (I flew that way BOS-SNN once on a traditional 757 where the seats in F were sold for the same price, but I think could be reserved in advance only with status), so they can play there kinds of tricks (treat true premium economy as more MCE seats, for example, when the plane is booked on a purely domestic routing) when these planes are put on domestic flights.
AA's true premium economy is only going into longhaul planes, but longhaul planes are not used exclusively on international routes. Sometimes that make connector flights within the USA to make better use of airplane (because turning around at the first USA entry point would require sitting in a hangar for too long).